Recovery of alcohols from olefin



March 9, 1943. H. M. GUlNbT 2,313,196

RECOVERY 0F LCOHOLS FROM OLEFINE HYDRATION PRODUCTS Filed Aug.. 15, 1959 Wash/'ng Tower' Alca/1d sag/fm 22 Patented Mar. 9, 1943 AUNITI-:o STATES nsoovnar or aLconoLs FnoM omrm maa'rrowrnonucrs Henri Martin Gulnot, Niort, France; vested in the todian Alien Property Cus Appucaucn August 15, 1939, sensi Nc. 290.311

. In France September 7, 1938 .1 claim. (ci. aso-64s) This invention relates to the recovery of alcohols from olen hydration products.

It is known that olens such as ethylene, n

propylene and the butylenes can be hydrated to give alcohols in the presence of certain hydration catalysts, such as sulphuric acid. Various authors have shown that, under certain conditions of acidity and temperature, it was possible to eliminate the alcohol from the reaction lvessel by entra'ining or by distillation.

In a recent patent speclcation of application `Serial No. 240,593 the applicants'have emphasised the necessity of not allowing the hydrating bath to increase considerably in alcohol content in order to avoid secondary reactions which lead Afinally to loss of yield and which are indicated by destruction of the hydrating reagent, in other words, it is necessary to eliminate the alcohol from the reaction bath as soon as it is formed. The applicants had found that this was an essentiakcondition for the satisfactory operation of the process.

It has previously been proposed to pass a mixture of olefin andwater vapour under pressure into an acid catalyst at a suitable concentration,

, and to cool vthe resulting gases to separate therefrom, by condensation, the` entrained alcohol, before returning them to the hydrating bath.

Now it has been 'found that in carrying out this previously proposed process the rapid elimination of alcohol from the hydrating bath takes place under-unfavourablel conditions, since gases charged with water and alcohol give up this latter with dimculty. 'In particular, when it is sought, as in the process previously proposed, to separate the alcohol contained in the gases by simple cooling, it is observed that only quite a small portion of the alcohol entrained in the body of circulating gases, .condenses, so that the residual gases returned to the hydrating bath cause the maior proportion of the alcohol which it was desired to eliminate, to accumulate in'this bath. There results from this not only a very reduced speed of production, but also the usual' disadvantages arising from an excessive proportion of alcohol in the hydrating bath, that is to say, the production of polymers, damage to the vbath and diminution of yield.

The following example shows the importance of the discovery set forth above.

1f 1000 m.3/hour of propylene are made to circalate through a hydrating bath formed by s.

ton of sulphuric acid of 60% strength` and raised to a temperature of 100, isopropyl alcohol is formed which is entrained, as soon as it iaproduced, by the unabsorbed gases. It is observed that in cooling the gases to 30 C. for example, in a water-cooled condenser, 180 litres per hour of an aqueous solution containing 9% of isopro- 'panol can be separated: but the gases which return to the circuit are saturated with the vapour emitted by these 9% alcoholic solutions, the-said vapours being about 60% isopropanol, so that if the gases leaving the condenser are submitted to a very intense cooling (down to about C. for example) another 90 litres per hour of 50% isopropanol solution are condensed. i. e.. 45 kg. of pure isopropanol.

'I'hus in the previous process, for 56.7 kg. o isopropanol obtained, 45 kg. or 80% oi' the whole return to the hydrating bath, whereas onlyv 11.5 kg. are retained by the water cooled condenser.

It will therefore be understood that the simple condensation at ordinary temperature specified inthe previous process is absolutely insumcient. and that it is necessary to take very feillcacious supplementary measures if it is desired to avoid the inconveniences mentioned above. As previously indicated, intense cooling ofthe gases is a possible way of removing the alcohol from the body of gases after leaving the hydrateing bath, but it would be quite diiiicult to carry out economically in industrial practice the cooling to '-15 C. of a considerable bodyof gas charged with condensable vapours and having a high latent heat. I Now it has been discovered that the alcohol may be separated from the .body oi' gases with which, in a vapour state, it is' mixed. ina manner which is both economical and eective by the use of a solvent which has a selective solvent capacity for 'alcohol as compared with oleiins.

According, therefore, to the present invention, V 40 there is provided a process of hydrating olenns by passing a stream of olefin-containing las through a hydrating bath, in which the alcohol entrained in the gases leaving the bath is separated therefrom by means of a solvent having a selective solvent capacity for alcohols as co i paredwtih oleiins. 1 The following are examples of solvents which can he used: pure: water, organic substances such as cresols and their homologues, the higher a1- cohols like cyclohexanol, glycol, glycerine, alone or mixed, salt solutions lsuch as solutions of calcium chloride,

The accompanying drawing illustrates diagrammatically a suitable arrangement of appass ratus for earning out the present invention, and

instead oi making a preliminary separation by condensation precede the washing. the condenser may be eliminated and a tower Il arranged in such a manner that it operates alone as an in- Jection condenser, in this case it serves at the same time for cooling the gases. for condensing .the vapours and for extracting the alcohol. How-- ever, the quantity of washing water which it is normally necessary to use to obtain an alcoholic Example 1 y 1000 :n.3 per hour of ethylene are circulated in a bath formed of 72% sulphunc acid heated to 130 and there is thus formed l1 kg. per hour of ethyl alcohol. l

By making the gases leaving the reaction ves- .sel pass into. a tower supplied with water and operating like an injection condenser the l1 vkg. of alcohol are withdrawn in the form of a 5 Gay Lussac solution where as if operation had 1 been by simple cooling of the gases to 30C. there solution oi suillciently high concentration at the base of the tower will be too small to absorb the excess oi' calories brought over by the gases and vapours. It is therefore advantageous to utilise for this purpose the alcoholic solution itself in `accordance with the arrangement described below and illustrated.

At the top of the washing tower I4, there is introduced by the pipe Il a convenient quantity of solvent (water for example) which circulates in counter-current in relation to the gases and vapours coming from the reaction vessel (not shown) and which enter the tower at 9. 'I'he alcoholic solution which flows away at the base oi the tower through the tube I0 is taken by a pump 20, cooled in a heat interchanger 2l and returned to the tower at 2l. This alcoholic solution thus circulates in a closed circuit in the lower zone of the washing tower where it ensures order to be returned to the hydrating circuit.

'Ihe two following non-limitative examples will make the operation of this process oi' alcohol elimination, more clearly understood.

would only have been separated 4.8 kg. of alcohol.

. Example 2 I 1000 m.3 per hour of propylene are circulated in a bath formed by a ton of 60% sulphuric acid heated to 100, from whence they emerge charged with 54 kg. of isopropanol. These gases are washed with 500 kg. per hour of butyl cres'ol in the washing tower I4, from the base of which there is withdrawn a 10%V solution of isopropanol which is separated from the butyl cresol by distillation. 1

What I claim is:

In a .process for the hydration of olefins which consists essentially in passing a stream of olencontaining gases through an acid hydratlng bath. the steps of passing Vthe mixture of vapours and gases leaving the bath through a tower in which it passes in counter-current to a solvent selected from the group consisting of water, cresols and their homologues, higher alcohols and mixtures thereof, withdrawing the solutionof alcohol in the solvent used at the base of said tower, cooling said solution in a heat interchanger, return- HENRI MARTIN GUNOT. 

